The present invention refers to an arrangement for preventing rattling caused by the synchronizing ring of an unengaged gear in a synchronized gear box and particularly to means preventing that ring from rotating back and forth freely on the shaft.
The object of such an arrangement is to prevent rattling noise being generated by a synchronizing ring for an unengaged gear in a synchronized gearbox. When the gear is not engaged, the synchronizing ring is designed to be capable, within a certain rotation angle range, of rotating relative to the synchronizing sleeve with which the synchronizing ring cooperates. The synchronizing ring is thus arranged loosely between a synchronizing hub arranged non-rotatably on a shaft incorporated in the gearbox on one axial side of the ring and a synchronizing cone (clutch ring) located on the other side of the ring and which is supported for rotation on the shaft and is intended to be connectable through the axially movable synchronizing sleeve to the synchronizing hub for the purpose of torque transmission. The synchronizing sleeve is supported in a conventional manner so as to be movable axially on the synchronizing hub. A conventional gearbox in which the invention is disposed may have a respective gear and a respective synchronizing ring on one axial side of or on both axial sides of the hub.
State of the Art
Modern synchronized gearboxes are provided with some kind of locking mechanism to prevent any possibility of the axially movable synchronizing sleeve of the synchronizing arrangement being brought into engagement with clutch teeth on the synchronizing cone of the relevant gearwheel before perfect synchronization is achieved between the relevant shaft and the gearwheel that has to be coupled to the shaft. These clutch teeth may either be arranged as a rim of teeth on a separate synchronizing cone which is fastened to the gearwheel or may be situated on a synchronizing cone which is integrated with the gearwheel. Axially outside this toothed rim, the gearwheel has an external, conical, tapering friction surface intended for synchronizing frictional cooperation with a corresponding internal, conical surface of the adjacent synchronizing ring.
When the conical inside surface of the synchronizing ring which has this internal configuration and is normally fitted loosely between the synchronizing cone and the synchronizing sleeve comes into frictional contact with the conical friction surface of the synchronizing cone, the synchronizing ring is rotated to a locking position (also an end position) in which locking teeth or claws on the synchronizing ring prevent axial movement of the synchronizing sleeve towards the toothed rim of the synchronizing cone so long as there is a difference in speed between the shaft bearing the synchronizing sleeve and the relevant gearwheel. When the speeds (rotation speeds) of these two parts have become fully equalized, i.e. when the synchronization is completed, the synchronizing ring is rotated back somewhat so that the axially extending internal ridges or teeth/cogs of the axially movable synchronizing sleeve can slide past the locking teeth of the synchronizing ring and continue until they engage the teeth in the torque-transmitting toothed rim of the synchronizing cone or, where applicable, of the gearwheel, thereby achieving the intended mutual connection of the shaft and the gearwheel.
However, a problem with this known design is that when the shaft is not engaged, the synchronizing ring generates rattling noise due to being fitted loosely between the synchronizing cone on the gearwheel and the synchronizing sleeve. This loose state, via the shaft and other connecting parts, subjects the synchronizing ring to torsional oscillations originating from the engine as a result of the ignition pulses in the cylinders. This rattling noise occurs when the synchronizing ring rotates to and fro between its end positions. The problem of course only occurs when the shaft is not engaged, since when the shaft is engaged, the synchronizing ring is in fact clamped firmly by the synchronizing sleeve. the problem is most obvious at low engine speeds. At higher engine speeds and higher vehicle speeds this rattling noise is in practice swamped by other more powerful sounds.
A prior design for dealing with this problem is known from U.S. Pat. No. 3,228,499 where the synchronizing ring is kept centered and fixed in position relative to the synchronizing sleeve by means of axially acting spring devices arranged between the synchronizing ring and the adjacent gearwheel. However, that design requires the synchronizing arrangement to be provided with special spring devices which, at one end, are fastened in axial bottom holes in the gearwheel close to the hub portion of that wheel and, at the opposite end, are accommodated in axial plugs on the outside of the synchronizing ring. Both the gearwheel and the synchronizing ring therefore have to be designed in this special manner and the spring devices also require a considerable space between the gearwheel and the synchronizing ring. Without being considerably redesigned, conventional synchronized gearboxes can therefore not be provided with this known type of spring devices to stabilize the synchronizing ring.